"Typically for any material, you change the temperature and you measure the number of electrons in a given orbital, and it always stays the same," Shen said. "But people found that in some of these materials, like the particular compound we studied, that number changed, but those missing electrons have to go somewhere."

It turns out that when the compound is heated, the electrons lost from the ytterbium atom form their own "cloud," of sorts, outside of the atom. When the compound is cooled, the electrons return to the ytterbium atoms.

"You can think of it as two glasses that contain some water," Shen said, "and you're pouring back and forth from one to the other, but the total amount of water in both glasses remains fixed."

This phenomenon was first proposed by 20th-century Russian physicist Evgeny Lifshitz, but an answer to the electron mystery hadn't been proposed until now."